Method of forming hollow vessels



R. G. GUTHRIE METHOD oF FORMING HOLLOW vEssELs Jue 29, 1937.

Filed Jan. 15, 1935 Patented June 29, 1937 APATENT OFFICE 2,085,313METHOD F FORMING HOLLOW VESSELS Robert-IG. Guthrie, Chicago, lli.,assignor, by mesne assignments, to Reconstruction Finance Corporation,Chicago, lll., a corporation Application January 15, 1935, Serial No.1,918

12 Claims. f (Cl. 113-112) My invention relates in general to thejoining of materials and particularly to brazing sheet metal parts inmaking shell-like housings, such as, for example, evaporator units forrefrigerators.

accomplished in a reducing atmosphere.

Another important object is to employ, during brazing operations, asubstance adapted to evapocompletely, and to the exclusion of gaseousmedia detrimental Still another object is to utilize a metal, readilyevaporable at brazing temperature, to develop vapors adapted to inhibitoxidation at vicinity of the braze; a utilize zinc i'or this purpose.

-A still further object is to regulate the pressure."v4 developedY infor the restricted escape, from the vessel, of vapors developed thereinin excess of oxidation inhibiting requirements.

, Yet another object resides in providing an improved shell-likestructure having brazed seams made inaccordance with my improvedantimedium I i interposed blanket of zinc vapor Figures 2, 3, and 4 showsheet metal parts of as well as a nished evaporator comprising a hollowvessel made from the parts by applying my improved technique.

To illustrate my invention, I have shown a 5 that is to say, by causingthe material of the parts,

at their abutting portions, to become integrated as by heating to causethe material to form solid solution one with the other or both with anintermediate brazing material.

The mechanical strength and leak-proof qualities of a jointor seam madein this fashion are or may be seriously impaired if oxidation oi' the 15parts occurs at the joint during the formation of oxidizing agency, suchas air, to the parts being joined during the progress of the brazingoperation. Y

For this purpose, I may employ any suitable material capable ofdeveloping an anti-oxide blanket under brazing conditions. I prefer.however. to employ zinc which readily vaporizes at a rapid rate atbrazing temperatures and will generate, in large quantities, comparedwith its volume 3o before evaporation, zinc vapor in suicientconcentration to blanket the parts being joined and inhibit theoxidation oi' the same. Zinc vapor, however,4 does H not interfere withthe vorderly formation of the braze. 'I'he metal parts I3 and I 5 to beconnected may be assembled together with a suitable brazing between theabutting por-A tions to be joined. The brazing medium may be copper, ora cuprous allo such as bronze or 40 brass, or other suitable brazingmaterial adapted, when heated, to unite with the material of the partsI3 and i5 and I may develop the gaseous anti-oxide blanket from asuitable material incorporated in the brazing material I1 as by using 45a brazing material comprising an alloy excessively rich in zinc, which.when the bramng material is heated to brazing temperature, will bevaporized out o1' the material and produce a protective at and aroundthe joint. not to rely upon zinc vapor I prefer, however,

`evolved from the brazing material, even when the same containssubstantial quantities oi' evaporable zinc but to deposit, in theinterior of the shell being brazed, a quantity or tree zinc I9,

' izing temperature of f gases in volume many 2 preferably in the formof powderor pellets of the pure metal. The purity of the metal is, ofcourse, relative but the material `should at least contain no impuritieswhich, when vapor' ed, might effect the brazing operation.

As soon as the shell is heated above thevaporthe blanket forming mediumI9, which temperature is, of course, below the temperature necessary tofuse the brazing material I1 and accomplish the braze, the material I9will evaporate and develop quantities of vapor within the shell II.Enough of the medium I9 is used, depending, of course, upon the size ofthe shell, to ensure the liberation of enough vapor in the chambrtoexclude entrance of atmospheres capable of impairing the braze eitherthrough the joint or through any openings in the chamber walls.

Zinc and other media, which may be used for the purpose of excludingdeleterious gases from the braze, of course, when vaporized, developtimes that of the initial volume of the material deposited in the shell.Consequently, it is desirable to have one or more' vent openings 2|,through which the excess gases may escape in order to relieve gaspressure within the shell; otherwise the accumulation of. gas within theshell may destroy the brazed seal by blowing out the brazing material I1while the same is in molten condition during the formationY ofthebraze'. These openings may be of restricted size in order to prevent thetoo rapid escape of the gases and to hinder entrance of gases injuriousto the brazing process. The size of the openings is not, however,critical and brazing may beperformed on shells having relatively largeopenings providing, of course, that enough of the gas-producing mediumI9 is employed to ensure against entrance of undesired gases into theshell.

'I'he invention may, of Vcom'se, be `utilized to advantage in anybrazing operation performed upon articles susceptible to the entrapmentof,

the blanketing gases at and in the vicinity of theV braze. I iind,however, that myA new brazing technique is particularly well suited tothe fabrication of sealed vessels of the type adaptedfor use asevaporators in refrigeration systems, and, in Figures 2, 3, and 4, Ihave illustrated parts of, as well as va complete, evaporator' II, whichmay be fabricated by' sealing together, by my improved brazingtechnique, preferably sheet metal pieces I3 and I5, to form a vesselcomprising an evaporator space defined by and between the pieces.

The pieces I3 and I5, of course, may be configurated'to any suitable orpreferred shape in any convenient fashion as, for instance, by pressingin adie. Preferably one of the sheets is formed with spaced depressions25 near the opposite end edges of the sheet, and onel of. the -Isheetsis provided with a series of parallel ductforming grooves 21 sothat when the sheetsare fastened together, the depressions and groovesform spaced header chambers 29 interconnected by a plurality of parallelducts 3l. The depressions 25 and the grooves 21 are preferably formedthe material of er-forming depressions and interconnecting grooves.

The sheet I5, also, is preferably formed with depressions 35 in positionrespectively opposite the depressions`25 so that the depressions 25cooperate, in the evaporator unit respectively, with the depressions 35to form the elongated cylindrical header chambers 29. One of the sheets,preferably the sheet I5, isalso formed at intervals with'depressions orgrooves 31 forming ducts 39 intersecting and communicating lwith theducts 3l.

The formed plates I3 and l5 are assembled in facing relationship with alayer of a suitable brazing medium 4I, such as copper, brass, or thelike, interposed between the adjacent surfaces of the plates which areto be secured together. A suitable material 43, such as zinc, isdisposed in the refrigerant space defined between the assembled plates,the material 43 being preferably arranged in the header portions 29. Theassembly then is heated, as by placing the same in a suitable furnace,in order to form, between facing surfaces of the plates I3 and I5, asolution comprising the material of the plates and the layer 43.

In order to bring these materials into solution, it is necessary toapply sufiicient heat to cause the material 4I, and/or the material atthe facing surfaces of the plates being joined, to melt so that thebonding solution may be formed by and between the facing surfaces ofsaid plates.

The bonding solution, of course,` will freeze between the plates andintegrate-said parts as lsoon as the temperature, at which the braze isformed, is reduced. The material 43, however, during the application ofbrazing heat to the blank, will evaporate and produce a gaseousatmosphere within the header portions 29, which atmosphere willpenetrate between the facing surfaces being joined as well as into theducts prises zinc, the presence of zinc vapor,.between the surfacesbeing joined, will not impair the joint or interfere with the formationof the same, since' the zinc may be absorbed by the jointformingmaterials so that at least some of the gas may condense in and form apart of the joint.

VIn order to prevent pressure of the blanketing vapor, developed withinthe refrigerant space, from becoming excessive, perforations 45 and 41may be formed in the header-forming portions 35, and an opening leastone of the ridges 31 in order 'to permit the vapors to escape at arestricted rate -so that excessive pressures will not develop within theevaporator. 'I'he openings 45, 41, and 49, however, are of such a sizethat the gases may' not escape so quickly as to decrease the blanketingatmosphere within the refrigerant sp;.ce to a point where deleteriousmaterial mayV enter. It will Ibe appreciated that the perforations 45,41, and 49 are preferably arranged in the relative positions thusdeveloped in the refrigerant` 49 form'ed in the end of at deleteriousgases.

After the formed refrigerating chamber.

'Ihe evaporator also is provided let tting 51 may, of course, beconnected in either or both of the headers, but I prefer to connect itin one ofthe header chambers 29, and to interconnect the header chambersby means of a conduit 59 fastened to and between the header formingportions 35 whereby gasied refrigerant collecting in one header chambermay escape through the conduit 59 into the other header and antconducting function, increases the strength and rigidity of theevaporator by assisting in holding the spaced walls I rigidly in spacedrelationship. The conduit 59 also provides a convenient handle forcarrying the evaporator unit and holding the same in position while itisbeing assembled in the cabinet.

It is thought that the invention and numerous of its attendantadvantages will be understood from the foregoing description and it isobvious preferred modes and forms herein described being merely for thepurpose of illustrating the invention.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is as follows:

being adapted to inhibit oxidation of the material of said tion.

2. 'I'he method of forming hollow vessels by Joining a plurality ofparts, which comprises arranging `the parts in vessel-forming position,heating the same to develop a solution of the parts at' and betweenadJacently arranged portions thereof whereby to integrate the parts, atsaid portions, while maintaining, within said vessel, an atmospherecomprising vaporized zinc at a pressure greater than that prevailingoutside of the hollow vessel, said atmosphere being' adapted to blanketthe portion entering the solution and excluding access of oxidizingmedia thereto during the formation of the solution.

3. 'I'he method of forming hollow vessels by joining a plurality ofparts, which comprises arparts in vessel-forming position, heating thesame to develop a solution of the parts vessel, a gaseous atmosphere ata pressure greater than that prevailing outside of the hollow vessel,

parts during the formation of the solu-Y said atmosphere being adaptedto inhibit oxidation of the material of said parts during the formationof the solution therebetween, and also providing for the escape of saidgenerated atmosphere, from the vessel, at a rate such as to maintain, atall times, solution, a suiiicient quantity of atmosphere to prevententrance of gaseous media capable of oxidizing the materials enteringsaid solution.

5. The method of forming hollow vessels by joining a plurality of parts,.which comprises arranging the parts in vessel-forming position, heatingthe same to develop a solution of the parts at and between adjacentlyarranged portions thereof whereby to integrate the parts, at saidportion while generating, within said hollow vessel, a gaseousatmosphere ata pressure greater than that prevailing outside of thehollow vessel, said atmosphere being adapted to inhibit oxidation of thematerial of said parts during the formation of the solutiontherebetween, and also providing for the regulated escape oi saidgenerated atmosphere from the vessel at a rate suflicient to prevent gaspressure, within-the vessel, from becoming great enough to disturb theintegrated l the formation of said solution, while maintaining in thevessel, at all times during the formation of the solution, a suirlcientquantity 'of the generated atmosphere to prevent entrance 4into thevessel ofl gaseous media capable `of oxidizing the materials enteringsaid solution- 6. The method of forming hollow vessels by joining aplurality of parts, which comprises assembling the parts in vesselforming position with portions of said parts in engagement in positionto form seams, introducing into the vessel a material adapted, whenheated, to produce a vapor within the vessel capable of excluding oxygentherefrom and from said seams, and then heating the vessel in order tovaporize the material and to integrate the engaging portions of said`parts by developing a solution of the material of the parts betweensaid engaging portions in the vaporous atmosphere formed by thevaporization of said material whereby to inhibit oxidation of saidsolution duringthe formation of said joint.

'1. The method of forming hollow vessels by joining a plurality ofparts, which comprises assembling the parts in vessel-forming positionwith co-operating portions of said parts in co-operating position toform seams, introducing, between said io-operating portions, a materialadapted to form a solution with the material of said-co-operatingportions and also at least partially evaporable to produce a gaseousatmosphere at a pressure greater than that prevailing outside of thehollow vessel, said atmosphere being within the vessel in position toblanket the co-operating parts and the remainder of said material inorder to inhibit l oxidation of the solution during the formation of thejoint.

8. The method oto 'g hollow vessels by joining a plurality o! partscomprising material adapted to alloy with zincl which consists inassembling the parts in vessel-forming vposition with co-operatingportions of said `parts in cooperating'position to form seams,introducing a bonding material comprising zinc between said co-operatingportions, introducing zinc within satd vessel, and then heating thevessel in order to vaporize the zinc within the vessel and to integratethe co-operating portions of said parts by developing a solution of thematerial of the parts with the zinc interposed therebetween, saidsolution being blanketed by the zinc vapor produced 5 by thevaporization of said zinc within the vessel whereby to inhibit oxidationof said solution during the formation of said joint.

9. The vme hod of forming hollow vessels by joining a plurality of partscomprising material adapted to alloy with another material, whichconsists in assembling the parts in vessel-forming position, withco-operating portions of said parts in co-operating position to formseams, introducing a bonding strip, comprising said other material,between said izo-operating portions, introducing a predeterminedquantity of said other material within said vessel and then. heating thevessel in order to vaporize the material thus introduced in the vesseland to integrate said cooperating portions by developing a solution ofthe material of the portions with the material of the interposedtherebetween, said s0- lution being blanketed by the vapor produced bythe evaporation of the material within the vessel in order to inhibitoxidation of said solution during the forming of said joint.

10. The method of forming a joint between elements comprising materialadapted to alloy with zinc, which comprises interposing a bondingmaterial comprising zinc between, co-operating seam-forming portionsheating to evaporate material adapted to provide an oxygen-excludingatmosphere at a pressure greater than that prevailing outside ofthehollow vessel, said atmosphere comprising an exin position blanketingsaid joint, and, at the same time, to permit the material of saidco-operating portions to form a solution with the bonding materialtherebetween.

ll. The method of forming hollow vessels by joining a plurality of partswhich consists in assembling the parts in vesselforming position withco-operating portions of said parts in position to form seams,introducing a predetermined quantity of zinc .within said vessel andthen heating the vessel in order to integrate the cooperating portionsof said parts to form a seam by developing a solution of the material ofthe parts therebetween and to vaporizc the zinc within the vessel underpressure to blanket the seamforming portions, whereby to inhibitoxidation thereof during the formation of said seam.

12. The method of forming hollow vessels by joining a plurality of partswhich consists in assembling the parts in vessel-forming position withco-operating portions of said parts in position to form seams,introducing within said vessel a material adapted when heated tovaporize and develop an atmosphere adapted to inhibit oxidation,thereafter heating the vessel in order to integrate lthe co-operatingportions of said parts by developing a solution of@ the material thereoftherebetween, and simultaneously to vaporize the material within thevessel to produce ,55 gaseous atmosphere under pressure in position toblanket the co-operating portions and thereby inthe Seam.

ROBERT G. Gufrnam. 70

